Surely at that point you haven’t written a setting, though? You’ve just written the word “everything” on a sheet of paper?
Look I can write a Game of Thrones (since the example is currently in use in the thread) settings and I can write it in such a way so that I denote that all the main characters are human. That all the generic NPCs are human, that all the kindgoms are run by human, but I can do that without simultaenously saying "no elves". I may not have written any in, but I there's nothing in the book that say you
can't be one.
Maybe some creative DM thinks the Lannisters would make good elves, and the Dothraki could be orcs. Someone might find Game of Thrones vastly more interesting if Tyrells were Elves, if the Dorns were Yuan-ti, if the Pykes were genasi and *drumroll* the Targarians were dragonborn (please pardon my name misspellings here, I'm not looking them up as I go).
I don't like books and settings that say "NO YOU CAN'T DO THIS!". I like books and settings that are written a certain way and are not preventative to alteration. It's not terribly difficult to include a sidebar saying "Hey guys this is how I imagined this setting, but if you feel something could be more interesting for your group by being changed, feel free to do so." Without saying that it's left open to interpretation, which is fine as well. But you have to
choose to say "No gnomes allowed!" or not. That's a choice the author had to make. It's a choice I don't tend to approve of and one, if I like the setting enough, will ignore.
As I said about Star Frontiers: if you can keep the theme and the feeling of a setting but make interesting changes to it, I'm really much more interested in "Creative Take On Old Property" than "Hey Look We Reprinted The Thing". I don't need a new copy of an old book. But I will buy a new twist on an old concept.
EX: I don't like dwarves. I tend to simply not include them in my games. But if someone
really wants to play a dwarf, I'll figure out how to make room. It's
easy to say "NO". It's more fun to say "Yes but..." in which case I have made a wide variety of non-typical dwarf options available (if someone wants to play a bearded racist parody dwarf, I will tend to ban that, which is sadly, the most common type of dwarf).